1. Field of the Invention
The present invention relates to a media-agitation type wet disperser which performs continuous dispersion treatment.
2. Description of the Related Art
Wet dispersion treatment is a treatment of finely pulverizing solid particles in slurry, thus to obtain dispersion containing further finer particles. The treatment is applied in a wide range of fields such as, for example, printer's ink, paint, polymerization toner, color resist, ceramics fine particles, titanium oxide, metal powder, and pharmaceuticals. These are slurry containing inorganic fine particles, organic fine particles, inorganic-organic composite fine particles, or mixture of them.
The media-agitation type disperser is a kind of device applied to above treatment. This type of disperser agitates a slurry treatment liquid and media together in a vessel, hereby pulverizing the particles through the use of the shearing force of the media and dispersing them. The treatment liquid after dispersion is separated from the media by a separator in the vessel, and is discharged from the vessel. A common separator includes sieve type such as gap type and screen type.
The performance of dispersion treatment is significantly affected by the diameter of applied media. Since smaller diameter of the media brings the diameter of the fine particles in the dispersion smaller, recent applications tend to adopt smaller media diameter. Reduced diameter of media, however, raises a problem of segregation phenomenon to forcefully push the media toward the discharge side. To solve the problem, Patent Document 1 proposes a media-agitation type wet disperser having less than 1 in L/D.
As illustrated in FIG. 9, the media-agitation type wet disperser 101 described in Patent Document 1 has a cylindrical vessel 102, a cylindrical separator 103 which divides the vessel 102 into an inner chamber 121 and an outer chamber 122 in the diametral direction of the vessel 102, with pluralities of slits 131 on the separator 103 connecting both chambers each other, a rotary shaft 104 rotatably positioned passing through one side of the vessel 102, a rotor 105 which rotates while being fixed to the rotary shaft 104, a feed opening 106 for the treating material, located at the other side of the vessel 102 and connecting the inside and the outside of the inner chamber, and a discharge opening 107 for the treated material, located at the outer periphery of the vessel 102 and connecting the inside and the outside of the outer chamber.
When the rotor 105 rotates while feeding the treating material from the feed opening 106 into the vessel 102, the treating material is agitated together with the media in the inner chamber 121, thus subjected to pulverization and dispersion treatments, then the mixture flows outward from the center of the vessel 102 therefrom, the slits 131 on the separator 103 separate the media, and finally the treated material is discharged from the vessel 102 via the discharge opening 107 on the outer chamber 122.
The disperser 101 can prevent the segregation of media by decreasing the L/D ratio and by increasing the surface area of the separator 103. The disperser 101, however, has a problem that the media positioned between the rotor 105 and the separator 103 tend to induce group motion there together, which leads to a problem of decreasing the shearing force among media, required to be generated around the rotor 105, thus causing lower treatment efficiency. Also there occurs a problem that media contacting with the surface of the separator 103 reach high speed which is close to the peripheral speed of the rotor 105, which results in wear of the separator 103.
[Patent Document 1] Japanese Patent Application Laid-Open No. 10-15411